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FAA Flammability Certification of Electrical and Electronic Components

Kendall D. HesterJames M. Peterson

Boeing Commercial Airplanes Group

International Aircraft Fire and Cabin Safety Research ConferenceOctober 22-25, 2001

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Boeing Goals• Comply with Regulatory Requirements • Continuously Improve Safety of Flight• Utilize Supplementary Internal and Industry

Standards • Improve procurement cost of equipment

– Utilize industry data – Use engineering skills and experience– Work together with our suppliers– Eliminate unnecessary and non-value added processes

and testing

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Typical Elements of Electronic Equipment

• Electric Wire• Printed Wiring Boards (PWBs)• Cathode Ray Tubes• Liquid Crystal Displays • Transformers• Switches• Small Components (Diodes, Resistors, etc.)

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Typical Electronic Equipment in a Jet TransportCooling holes

Circuit cards

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Typical Printed Wiring Assembly

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History of Electronic Equipment Usage in Commercial Transport Airplanes

• In the early years, electronic equipment consisted primarily of simple avionics in the flight deck and E/E bay

• Later, additional electronic units and sensors were added all over the airplane

• In recent years, there has been a great expansion of in-flight passenger entertainment systems, up to Internet access on seat-powered laptop computers

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Electronic Equipment Design Criteria

• Military specifications used to control the fire properties of electronic equipment.

• Many of these military specifications have been recently canceled.– Example older requirement - Printed Wiring

Board material shall be epoxy/glass (Type GF) or other material with equivalent or better temperature, arc, and flame resistance, in accordance with MIL-P-13949.

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FAA Flammability Requirements

• FAA regulations were changed in 1967, and new flammability requirements and test methods were added– New standards for side-walls, ceilings, etc.

• Small parts did not have to be tested – Except for small parts (such as …… small

electrical parts) that would not contribute significantly to the propagation of a fire…

• Electronic components were viewed as “small parts”

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FAA Flammability Requirements (cont)

• In the 1960’s, there were only a few electronic components in the EE bay and flight deck. – Only materials compliant to the Military Standards

(self-extinguishing) were used• Today significantly more electrical/electronic

components are used• Military production standards have been

canceled and replaced by industry production standards

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FAA Flammability Requirements (cont)

• Aerospace industry standards require either– IPC 4101 flammability test be done on laminates

making up a PWB before board is assembled or– UL 94 V0 test on the finished PWB– No industry requirement for 12-sec vertical

• FAA clarified that regulatory testing of electronic components requires

– FAR tests - 12-sec vertical Bunsen burner test (e.g., printed wiring boards, PWBs)

– or approved alternatives

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FAA Flammability Requirements (cont)

• Aerospace PWBs built to industry standards always pass FAA test with high margin

• FAA receptive to “equivalent safety finding” to approve PWBs meeting industry standards without requiring FAR 12-sec vertical test

• FAR 21, § 21.21(b)(1)– …. any airworthiness provisions not complied with

are compensated for by factors that provide an equivalent level of safety …

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Equivalent Safety Finding

• Plan for establishing equivalent safety finding– Analysis of IPC, UL, and FAR test procedures– Analysis of the sample testing by suppliers

(i.e. the on-going process control)– Test a representative sample of IPC and UL compliant

PWB materials using the FAR 12-sec vertical test• Bare printed wiring board laminates• Complete multilayer printed wiring boards• Printed wiring assemblies with conformal coat

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FAA Flammability Requirements (cont)

• When an “equivalent safety finding” is granted, PWBswill be FAA-approved by process control

• Showing compliance by process control is a significant need for electronics – Electronics are in constant redesign

• Testing by part number is inefficient and extremely expensive in the long run

– Continuous process control provides better assurance • As opposed the current one time test

– Most electronics redesign does not change materials• Re-layout of PWBs and microcircuits• Software updates

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Reasons for Electronic Redesign

• Airline requests for increased functionality– More features and options – In-flight entertainment

• Product improvements– Updates, problem resolution, production

improvements• Component obsolescence

– Cancellation of the military specifications– Commercial components have a shorter production

life due to high volume users

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PWBs are the Most Frequently Changed Item

Typical Materials Redesign ImpactsSmall electrical components:

Microcircuits, resistors,capacitors, switches, etc.

Frequently changebut small are parts

Flexi-cables, small wire cables Seldom changeDisplays Seldom changeGaskets Seldom changeConnectors Seldom changeSheet metal, screws, etc. No impact on the

flammability analysisPrinted wiring boards Frequently change

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Process Control Methods

• Boeing is incorporating process control methods for design and manufacturing – DO-178 (Example of Software process control) – DO-254 (Example of hardware process control) – ISO-9000 (Example of quality by process control) – AS-9000 (Example of quality by process control)

• Process control provides– Improved quality, reliability, and performance– Lower costs– Shorter design cycle times

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Use of Industry Standards

Conformalcoating registered

& tested UL 94 V0 ?

NO

YES

NO

FAR 25Flame Test

NO

YES

Flame Test Report

Design for a PWB

YES

PWB Laminates

registered & tested per IPC 4101 or

UL 94-V0?

*BOM = Bill Of Materials

Flammability Assured

BOM* Analysis Documented

IsPWB

registered & tested per UL 94- V0?

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Conclusions

• The FAA requires data for flammability certification of electronics before E/E components can be delivered on airplanes.

• Currently, all affected parts must be tested to 12-sec vertical for flammability certification

• Suppliers of E/E equipment need to put a priority on acquiring acceptable data far upstream of delivery.

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Conclusions (cont.)

• An alternative method for flammability certification is urgently needed

• Boeing is working with the FAA to establish an equivalent safety finding to enable certification by process control using existing industry standard test processes instead of testing each PWB